Abstract：A 3-dimension pump model which has the same size as the real pump is built in CATIA software.Tetrahedron element is uscd for the finite element method. The method overcomes the approximation of using shell element and thus makes the result more reliable. The strength of auxiliary reactor pump is calculated under seismic load and temperature field. The maxim Von Mises stress is 15.8 MPa, which is smaller than strength 132.825 MPa. The auxiliary pump is safe and fulfills the requirement of standard document.